21745744 has 20 divisors (see below), whose sum is σ = 43161300. Its totient is φ = 10607360.

The previous prime is 21745733. The next prime is 21745769. The reversal of 21745744 is 44754712.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 12673600 + 9072144 = 3560^2 + 3012^2 .

It is a super-2 number, since 2×21745744² = 945754764227072, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15919 + ... + 17230.

It is an arithmetic number, because the mean of its divisors is an integer number (2158065).

Almost surely, 2^21745744 is an apocalyptic number.

It is an amenable number.

21745744 is a deficient number, since it is larger than the sum of its proper divisors (21415556).

21745744 is a wasteful number, since it uses less digits than its factorization.

21745744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33198 (or 33192 counting only the distinct ones).

The product of its digits is 31360, while the sum is 34.

The square root of 21745744 is about 4663.2332131258. The cubic root of 21745744 is about 279.1203002919.

The spelling of 21745744 in words is "twenty-one million, seven hundred forty-five thousand, seven hundred forty-four".